Higher Cryptogamia and the Phanerogamia. 447 



of spore has hitherto been found, is as yet obscure, but the 

 above observations have been made by MM. Hofmeister and 

 Mettenius, and so far as the existence of the jjrothallium with 

 the archegonia in Selaginellaj and the development of the embryo 

 at the end of a suspensor growing down from the prothallium 

 are concerned, I can confirm them from my own observations. 

 I have not yet succeeded in seeing the spermatozoid produced 

 from the small spores, which however I found burst and empty 

 among the germinating large spores. As the processes above 

 described occupy several months after the discharge of the spores 

 from the antheridia and oophoridia, there is some difficulty in 

 observing all the conditions. 



Hofmeister suggests, that in the genus hycopodium, where 

 there is only one kind of spore, 2. prothallium is formed, which, 

 like that of the Ferns, produces both archegonia and antheridia. 



The relations of the course of development here to what we 

 meet with in other families of the vegetable kingdom, will be 

 spoken of presently in a general summary. 



RHIZOCARPEiE, 



The morphological import of the two kinds of spores of Filu- 

 lariuj asserted by Schleiden, has proved correct, although his 

 views with regard to the nature of the process of impregnation 

 have been refuted. The small spores (described above as pollen- 

 grains) have been discovered to bear the closest affinity wdth 

 those of Selaginella and Iso'etes, since shortly after their emission 

 from the spore-sacs they burst and discharge cellules containing 

 spiral filaments {spermatozoids) (PI. XVII. C. fig. 1), which soon 

 break out and swim freely about in the water. The sacs w^hich 

 produce the small spores therefore represent the antheridia here. 



The archegonia are closely allied to those of Selaginella^ but in 

 Pilularia only one is formed on each large spore. The large spore 

 soon after it becomes free exhibits a cellular growth, forming a 

 prothallium analogous to that of Selaginella at its upper end, in 

 which a central large cell becomes visible. The cells of the pro- 

 thallium multiply, and it projects at its apex through the summit 

 of the spore, the triangular lobes of the spore-coat separating to 

 expose it. The four cells above the large central cell grow out into 

 papillae (which Schleiden mistook for pollen-tubes), and an in- 

 tercellular passage is produced leading down to the large central 

 cell, in all probability afibrding access to a fecundating sperma- 

 tozoid (PL XVII. C. fig. 2, 3). This single central axchegonium 

 very closely resembles those found in the analogous prothallia of 

 Selaginella and Isoctes. There is never more than one developed. 

 When the spermatozoids can have access, the large cell of the 



